Television apparatus



Sept. 16, 1930. P. CLARK TELEVISION APPARATUS Filed may 29, 1928 R E N E C E R Patented Sept. 16, 1930 UNITED STATES PATENT OFFICE PAUL LOVERIDGE CLARK, or BROOKLYN, NEW YORK TELEVISION ArrARA'rus Application filed May 29, 1928. Serial No. 281,567.

to improve delineation of both the transmitted and the received images, and to produce a high intensity of illumination on the ob ects and persons whose images are to be transmit-.

ted by television; and to provide means for simultaneously receiving without appreciable heterodyning both picture-point-frequency signals and audio signals, such as are translated into sound waves by a telephone receiver or loud-speaker, as understood in the art. Additional objects are pointed out in the specification, in the drawing, and in the appended claims, all forming parts of this complete disclosure.

I attain these several objects by the mechanisms and circuits illustrated in the accompan ing drawing, in which- The gure is a perspective'view showing a television transmitter and a television receiver comprising a complete television system except for the synchronizing and auxiliary circuits.

In this specification, the term audio frequency or low frequency means frequencies of less than 10,000 cycles per second or frequencies of a recurrent nature such as to produce an audible noise in a commercial type of telephone receiver or loud-speaker and delivered to such loud-speaker by energy amplified or controlled by a commercial or special type of radio receivin set, at the presenttime, such frequencies eing passed without undue distortion by radio sets equipped with iron-core transformers (known in the art, as audio or low-frequencytransformers); the term picture point frequency is used to denote the frequency of transmission and reception of successive points comprising a scanned view or field of exploration, as understood in the art, and it is not necessarily equal to the square of the number of lines transmitted, as defined by applicant in his pending application Ser. N 0. 162,311; but may be the frequency, either periodic or non-periodic, such as comprises sending pictures by the method of the Radio Corporation of America, in their recent transmission of views by the use of lines in parallel formation but of variable width to produce shaded areas, such as compose the likeness of President Coolidge, on page ,45 of the magazine All about television, published in August or September, 1927, by the Experimenter Publishing Company, Inc., New York. The terms Vertical and horizontal are here used for the sake of clearness, in referring to the drawing, it being understood that by shifting the apparatus through an angle of 90 degrees, or any other desired angle, the scope of this invention is not restricted. i a

The system herein-described may be used by .wireaswell as by radio-broadcasting, or by a combination of the two methods.

Referring to the drawing, it is seen that a motor 1, preferably rotating at constant speed and at more than 1800 R; P. M., is direct-connected to a shaft 2 on which is mounted a. gear 3 meshing with an idler gear 4 meshing with a gear 6 (or aperture disk) provided with a plurality of equi-spaced radially-disposed apertures 7, 7A, and rotating on a shaft, 8 running in a bearing 9, so that as the armature ofthe motor rotates at high speed, in the direction shown by the arrow 10, the disk 6 rotates in the direction shown by the arrow 11, so that rays (the axis of the cone or pyramid of rays being shown at 12) from the lamp 13'pass through successive apertures, as 7A, and continue on through a curved aperture 14 in an opaque plate 15 and traverse an arcuate area or line of travel sub stantially parallel to, or tangent to, a vertical plane parallel to the shaft 2. On the shaft 2 is rigidly mounted a cylinder-16 on which is disposed aspiral or worm 17 comprising a plurality of juxtaposed, concave, contacting reflecting surfaces or concentrating reflec tors 18, 18 18", etc., having conjunctive polygonal peripheries, and ground and polished on the spiral; so'that as the motor rotates, the spiral travels the same as a righthand screw and in definite'relation to the travel of the disk 6, the pitchof the spiral and the speeds, arrangement and disposition of coacting parts of the apparatus being such ously with the loss of registration of the rays on the. last mirror 18 of the spiral, the first mirror 18 is exposed to the rays by virtue of the fact that the aperture disk 6 will have rotated through the proper arc to present the aperture 7 B in the path of rays on a line connecting the lamp 13 and the mirror 18. A

spiral comprising two convolutions is shown and the gear 6 has twelve apertures, so that it is seen that for each two revolutions of the spiral, the geared disk 6 should make 1/ 12th of a revolution, so that the gearing between the spiral and the disk should be in the ratio of 24 to 1. The lamp 13 is stationary and should ordinarily be an arc-lamp enclosed in a light-tight housing (not shown), and all parts of the apparatus subject to irrelevant illumination should be blackened. A centrifugal switch 19 is-mounted on'the shaft 2 and connected to a relay 20 (through suitable slip-rings, not shown) the relay being connected in the lamp circuit, so that the circuit is opened except when the explorer is running at high speed, in order to prevent appreciable over-illumination on the field of View, this scheme being somewhat similar to that shown in Patent No. 931,036. A stationary or movable or rotatable chopper or interrupter 22 having alternate light-transmitting and light-absorption bars, 22A, 22B, which may be equally spaced or unequally spaced or distributed, may be placed either behind of or in front of the person or object to be televised or' scanned. These bars may be painted on a white surface in a series of black, red, or neutral color, or photographed on a clear glass or gelatlne plate or cylinder.

The dimensions of-this light-chopper, and.

its location and angle relative to scanning rays directed thereupon, should be such as to embrace all rays within the maximum angle subtended by the view transmitted, and should preferably be of even greater dimensions so as to affect all rays directed by the explorer, except those rays which are intercepted by the object, as 25, positioned in front of it, and upon which object the rays should be focused with great accuracy, it being considered that the delineation of the person 25 is of greater importance than that of transmitting an accurate image of the interrupter. As the scanning beams sweep over the person 25 and the screen or grid or chopper 22, it is evident that if the bars and spaces are of equal width, aseries of signals will be sent at .the frequency of traversal of the bars and apertures, as described in Patent No. 1,161,- 734, and in my pending application Ser. No. 162,311, so that if the chopper comprises say, 10 bars, and there are 100 traverse or vertical lines scanned'for each cycle of the spiral, then, the time for traversing each bar is 1/2000th of a scanning cycle; and if 10 pictures are scanned during each. second of time, it is seen that the frequency of each traversal is 1/20,000th of a second, which is twice the audio frequency of radio sets. As the beam sweeps over the object, as 25, this frequency will, ordinarily, be reduced, on account of the light and shade areas of the object not being in consonance with the chopper light and shade areas. However, if the scanning frequency of successive lines be sufliiently high, and each line he made up of a small number of light'and dark areas alternating,

icture si nal translatin means as under stood in the art, and will not influence the loud-speaker signals. shown, necessitates the illumination of the chopper 22 and the object 25 by means of a vibratory beam of concentrated light, namely, the scanning beam, and not by external illumination. It is, however, apparent that a photoelectric cell may be placed where the lamp 13 is shown, and the person and the grid illuminated directly by lamps, as understood in the art. \Vith the system, here shown, the person should subtend an area much less than the area of the grid or chopper 22, so that the effect of the impulses produced in the photoelectric cell 26 by the vibratory The system, here.

by the spirally arranged mirrors is more or less square, it is seen that even if the head occupies a large relative solid angle of the exploring system, the bars and white illuminated spaces will be transmitted over certain irregularly distributed portions of each picture cycle. The signals so sent may be uti: lized for the dual purpose of synchronizing and picture signals, as disclosed in my patent application, aforesaid. The screen or chopper 22 may be adorned with geometrical figures or designs having light and dark areas of a size enabling them to be more or less sharply scanned and reproduced at the receiving end of the apparatus, so that during changes of scene, such as caused by different persons appearing before the televisor and in front of portions ofthe chopper 22, a pleasing effect is secured, and a blank white or dark area is not thrown on the receiver screen 51. Also, large moving pictures or moving designs (not shown) may be automatically swung into the focal surface of the' scanning beam of the transmitter. The chopper 22 may be cylindrical in vertical cross-section and have a central recessed portion to fit around the back of the headialid shoulders of the subject 25, so as to secure extreme sharpness of delineation of the shaded areas on the said chopper and enable the scanning beams to focus fairl close on the said areas. A photoelectric ce 1 26 is located to receive light reflected from both the object 25 .a'nd the chopper 22 simultaneously with the illumination of each small scanned area of said object and chopper. This cell translates the light rays received by it into electric currents responsive to and in proportion to the shade of each small area and at a frequency'determined by the scanning rate, and these currents are transmitted through suitable amplifiers, modulators, broadcasting equipment 29, or wire lines (not shown), or any suitable combination thereof, to an amplifier, filter, reception-transforming or conversion system 110, 103, which is included in the circuit. A suitable lightvalve or neon lamp 32 is connected to the amplifier or filter 103, the characteristics being such that light rays (the'optical axis of which is the line 33) from the lamp 32 are proportional in intensity to the strength of the transmitted signals and simultaneous therewith, the chopper bar signals derived from the chopper 22 being received and projected upon the screen 51, in positions corresponding with the bars exposed to the scanning beam of'the transmitting apparatus, so that whatever signals affect the photoelectric cell 26 are projected by the mechanism comprising the complete receiving apparatus in correspondingly relative locations to delineate on the screen 51. an approximate or exact reproduction of the image at the distant sending station. The rays from the lamp are collected and focused by -a lens 34 upon a small area embracing the width or approximate width of a single picture line; at the point 35 on the mirror-36 comprising one of a plurality of contacting, equal size, preferably plane, mirrors on the polygonal mirror group 37 which is attached to a shaft 38 running in a bearing 39, and attached to a gear 40 which rotates in the direction of the arrow 40A and meshing with a gear 41 on a shaft 42 running in bearings 43 and attached to a'gear 44 meshing with the gear 45 which is mounted on the shaft 46 which runs in a bearing 47 coaxial with the armature of the'motor 48 i and driven by said motor, the motor also driving the cylinder 49 and the spirally arranged reproduction of the transmitted images, and

cause said images to focus acceptably on the focal surface or screen 51. This screen should be of such configuration and so placed relative to the scanning system that each pyramidal or conical pencil of light distributed by the element 50 falls upon the screen at a point at such a distance from the individual mirror in function, as to focus in a beam of minimum cross-section upon said surface. The screen may be concave incross-section and convex in longitudinal section, or of varia-ble curvature at different parts of its surface. The diameter of the beam at its intersection with the screen should be approximately equal to the distance between the centerlines-of two adjacent scanned lines of the image, such as are projected upon the screen by adjacent mirrors, provided the adjacent mirrors reflect light to adjacent lines. It is I evident that adjacent mirrors need not necessarily control the light to adjacent lines, but

to alternate lines, or to lines several spaces apart. The stator of the motor 48 is mounted in abearing 52 (somewhat similarly to the motor .mounting shown in Patent No. 1,666,594) 'for rotation coaxial with the shaft cal elements with the transmitter optical elements, by twisting the knurled member 53. Means for locking the stator relative to the bearing, is shown at 54, and may be either a screw or a spring-controlled member or ratchet so disposed as to prevent undesirable rotation of the stator due to back-thrust caused by the torque produced between the combination with the motor 48 comprises a part of a speed-increment deviceand is used for phasing, synchronizing or framing the picture on the screen 51, without upsetting;

, 46 and the stator may be rotated, for phas; r I ing or synchronizing the motor and the opti- .motor rotor andthe stator. The device 53 in isochronism, it'being assumed that the receiver and transmitter are functioning'isochronously described in my Patent 1,648,042. The screen should be of glass or gelatine and should be outlined with a dark border to pre vent the registration of rays reflected by,e1ements adjacent the element momentarily functioning for the production of the points comprising a single line of the view transmitted and received. It should be understood 6 that the chopper bars and the high-frequency signals produced responsive to their pres-" ence, and reproduced in the receiver,-arefor the purpose of producing many breaks,

above. audio frequency during the transmission of each Vertical line or horizontal line, in order to break up large uniform areas of a single or gradually-variable shade into a number of separate waves each of which may comprise a plurality of waves of radio fre quency. Any suitable system of gearing for securing proper speed ratios may be used.

' The cylinders, spirals and mirrors should be of metal, and made integral, the reflecting surfaces of the mirrors being ground, silvered and lacquered, and non-essential parts blackened, as is customary in making apparatus of the class, herein described. A twoturn spiral should make two turns for each picture transmission; a three-turn spiral, three turns; a four-turn spiral, four turns; etc., so that it is seen that if a spiral having a large number of turns be used it is necessary to speed u the motor several fold, or to provide suita le gearing between the motor and the scanner. Two or more spirals may be used on the same shaft, each adapted for a scanning operation characteristically suited to its design. The greater the number of spirals for a fixed number of mir-' rors, as, say, 100, the greater the angle each mirror subtends relative to the axis of rota- I tion, and the larger the picture reproducible. .3

But the greatest advantage lies in the fact that the size ofthe illuminant may be in creased several old by making the spirals up of a good number of turns. If the spiral has a single turn, a source of, say, 1 mm. projected area may be used; but if the spiral has ten turns a source of more than 10 mm. diameter may be used, and as the illumination varies as the square of the projected diameter of an illuminant, it is seen that more than 100 times the illumination is available for producing a picture, and hence, pictures of areas much greater than those at present being received on an apparatus including a neon lamp may be successfully and sharply illuminated. To be sure, each element or mirror is functioning the same length of time, say 1/10,000th of a second while it is sweeping a vertical line; regardless of whether there are 100 elements on a single spiral or 100 elements on a tenturn spiral which has an angular velocity ten .times as great as the single-turn spiral;

but the fact that each element on the tenvturn spiral .subtends an angle, relative to the axis of rotation, ten times as great as the angle subtended by each element on the single-turn spiral affects the angle of incidence of the limiting rays falling thereupon and presents a larger base for the cone or pyramid of incident or reflected rays. In .systems heretofore used the size of the received image, using a single neon lamp, has been of the order of two inches square; using a ten-turn spiral,as disclosed in this specification, it is feasible to produce a picture 20 to 24 inches square;

Ordinarily, a scanning system should embrace, say, a minimum of lines, vertically; by 50 lines horizontally; in order to secure 2500 picture areas or points, and assure good definition, and if the transmitted pictures are .to depict motion the speed of transmission should be about 20 complete frames or pictures per second, producing a line frequency of 20 50=1,000; and a unit, or picture point, frequency of 20 X 50 X 50 50,000; the latter figure being five times the audio range. By breaking up each line into 20 equal or unequal parts, half of which are black and half white, spaced alternately, as shown in Fig. 1, the scanning rate per line is 10,000 cycles and therefore just equal to the audio limits, and will cause heterodyning with the audio frequencies, and irrelevant sounds in the loudspeaker, provided the picture signals and the audio signals are being broadcast on the same wave length and are of approximately equal strength. Consequently, it is evident that in order to reduce or obvi ate the interference consequent to'heterodyning in the loud-speaker, a considerably higher picture point frequency, i. e., a frequency considerably above 10,000 cycles, is desirable. By using a chopper bar system in conjunction with the image of a person to be sent by television, the rate of the sending and production of picture signals, consequent to the eflect of the sweeping of the bars and spaces by a beam of light, may be increased in direct proportion to the number of bars. To be sure, the person seated in front of the device 22 is not composed of alternate light and dark spaces corresponding to those on the device 22; but asthe persons features and dress are more or less of a shaded or contrasting nature, a series of high-frequency impulses are produced merely by scanning the persons image, and neglecting the effect of the contrasting lines comprising the device 22, that is to say, we may reasonably assume that the scanning of a single line of the View embraced anywhere within the solid angle scanned by the explorer will consist of a given number, say, 5 areas of different characteristics; so that the transmission of the values of these areas will produce in the is obvious that the higher the picture point V frequency, the less effect the signals will have on the audio set, and if the filtering system be accurately and efliciently made, the audio signals will not produce inaccuracies in the pi cture-point values, or cause faulty registration on the screen 51. The number of mirrors comprising the polygonal mirror 37, and the speed of rotation of'this mirror should be such as to reflect the beam of light to follow the spiral in a line about parallel to the axis of rotation of the spiral, and the mirror 37 should rotate in a plane parallel to said axis;

each mirror, as 36, should subtend such an angle relative to the axis of the disk 37 so that, as the disk rotates, the light beam re-,

flected by any mirror falls upon two or more of the adjacent mirror-s of the spiral and does not simultaneously fall upon the mirrors comprised in adjacent convolutions. As the reflected beam 64 registers on the mirror at the end of the spiral, the next adjacent mirror on the disk 37 should just be entering the angle subtended by the extreme end mirror on the spiral; so that the process is continuous and the apparatus is optically operative 100 per cent of the time. The angle subtended by each mirror relative to the axis 7 38 of rotation should be approximately onehalf of the angle subtended by the extreme right and left mirrors on the spiral relative to the reflecting surface of the mirror, on the disk 37. The size'of the spiral'and coacting apparatus should be considerably larger for i use in the transmitter than for the receiver,-

principally on account of the low light values available for registration upon the cell 26, and it is evident that the larger the mirrors used on the spiral, the greater the intensity of the point of light available for sweeping the field. of view. Furthermore, the focal distances of the scanning elements of the receivershould ordinarily be of sometransmitting antenna, at either the same what different characteristics from those of the transmitter.

The microphone 30 is connected through suitable means 29, so as to broadcast over the wave length as, orat a different wavelength from, that employed for the picture-point signals, all signals or merely the signals for a single purpose being'received by the antenna at the receiving end of the apparatus.

What I claim is 1. Ina signaling system, the method of operatiornwhich consists in producing at a high rate of speed a great plurality of sue.-

. cessive signals of non-uniform duration, and

transmitting the signals of relatively long duration each in a period of time less than the period required to produce an audible sound.

2. A method in accordance with claim 1,

' i and in which signals of'proportional duration are transmittedin correspondingly proportional periods ofctime. 1

- 3. In a television system, the method of operation, which consists in transmitting non-periodic picture signals at a minimum frequency exceedin the maximum frequency of audible sign ransmission.

4. In a telev on system, the method of operation, which consists in producing nonperiodic picture signals au a minimum frequency exceeding the maximum frequency of audible signal transmission,

5. In a television system, the method of operation, which consists in deriving nonperiodic picture signals at a minimum frequency exceeding the maximum frequency of audible signal transmission.

6. In a television system, the method of operation, which consists in transmitting successive groups of television signals at a high frequency so that the frequency of grouptransmission is outside the range of audible frequencies.

7. In a television system, the method of operation, which consists in transmitting television signals at a frequency sufliciently high as to render the signals continuously inoperative for translation into sound waves.

8. In a television system, the method of operation, which consists in transmitting television signals continuously at a frequency sufficiently high as to render the signals in- "deriving, consequent to the scanning, signals each having characteristics which are affected by the average shade of a corresponding scanned strip and each of a duration which varies substantially in accordance jolntly with the length of the corresponding scanned strip and with the duration of the interval of time during which the strip is scanned; and in causing the scanningof a plurality of successive relatively long strips of contrasting shade to be effected at sucha rate of speed as to assure the completion of the scanning of the plurality of strips of contrasting shade in an interval of time of a duration shorter than the duration of an interval of time during which a sound wave may be produced.

10. In a television transmission system, in which'the television signals derived from an image or subject to be transmitted are of such recurrence, contrast and duration as to produce, at moderate transmission signaling speeds, a train of signals having characteristics rendering some of them operative for the production of sound; the method of rendering the signals inoperative for the production of sound; which consists, in transmitting the signals successively at a high rate of speed and at a high frequency, to cause the completion of the transmission of a plurality of successive, contrasting signals, each of relatively long duration, to be effected in an interval of time of a duration shorter than the duration of an interval of time dur ing which a sound wave may be produced.

111 In a television transmission system, in which the subject or image to be scanned is made up of image elements or areas of irregular dimensions and of contrasting shade; the method of operation; which consists in,

deriving signals each ofa duration substan- 1 I tially proportional to one or more dimen-c SlOIlS of a corresponding shaded area, and

transmitting the successive signals ata rate of speed and at a frequency sufiiciently high to assure that the minimum frequency of occurrence of successive signals is, greater than the frequency of sound waves.

12. In a television transmissionsystem, in which the subject or image to be scanned is made up of image elements or areas .Of irregular dimensions and of contrasting shade;

the method of operation; which consists in,'

deriving signals each'of a duration substantially proportional to one or more dimensions of a corresponding shaded area, and transmitting the signals in rapid succession at a frequency sufliciently high to effect the completion of the transmission of a plurality of cycles of signals in an interval of time of a duration shorter than the duration of an in;

terval of time during which a sound Wave may be produced. V p

13. In a'television system, in which the subject or image to be scannedris made up of image elements or areas of irregular dimensions and of contrasting shade;'the method of operation; which consists in, deriving signals each of a duration substantially proportional to one or more'dimensionsof a corresponding shaded area, transmitting and receiving the signals in rapid succession at'a rate sufiiciently high to assure that the minimum frequency of occurrence of consecutive signals is of a higher order than the frequency of recurrent sound waves,and apply-v ing the signals to reconstruct the image.

14. In a signaling system, the method of transmission; which consists; in transmitting at a high rate of speed and at a high frequency, radio signals successively of vari-v able strength; so that successive groups, each comprising a plurality of signals, are successively transmitted at a frequency sufliciently high to prevent interference with sound-reproducing apparatus.

15. In a signaling system, the method of transmission; which consists; in transmitting, at a high irregular frequency, successive signals having non-uniform characteristics; and causlng the duratlon of the transmission period of a group, comprising two or more signals, to be shorter than the period essential for the establishmentof a sound wave. In witness whereof, I hereunto subscribe my name this 20th day of Ma 1928.

'PAUL LovEmnc E CLARK. 

